Power divider circuit



1954 R. c. RAYMOND POWER DIVIDER CIRCUIT Filed Sept. 14, 1945 INVENTOR. RICHARD C. RAYMOND ATTORNEY Patented Jan. 26 1954 UNITED STATES hATENT OFFICE 8 Claims.

This invention relates to a radio frequency power divider circuit, and particularly to one where the power may be divided in any suitable proportion between two outputs withoutmaterially changing the combined impedances' of these outputs as seen from the input.

It is therefore an object of this inventionto provide a means for dividing in any suitable proportion the radio frequency power output to a transmission lines and'having incorporated therewith a means for regulating said proportion at will.

It is another object of this invention to provide a transmission line construction having an input line, and a Pair of output. transmission lines joined thereto with a means for dividing in. any suitable proportion the power output from each of said parallel output lines without materially disturbing the effective terminating impedance of said input line.

Other objects and features of the present invention will become apparent upon a careful cone sideration of the following detailed description when taken together with the accompanying drawing, where the figure illustrates an elevational vi-w generally in cross section of a typical embodiment of the invention.

The input transmission line, shownv at is expanded in partial cross-section by thetapered portion is before connecting with the output transmission lines El and. i8 at a stub-supported. joint ii) at which the short-cirouitcd stub transmission line so is adapted to act as an electrically resonant mechanical support in accord-- ance with well-known principles. A metallic rod 32 is mounted ooaxially with respect to the transmission lines Ti and 5'8, passing through asuitable aperture in the central conductor 83 of the transmission lines i5, '16, 813. In its central portion the shape of the rod 82, which is elsewhere cylindrical, is modified to provide a rack adapted to engage a pinion 85 mounted upon the shaft to, so that the rod 82 may he longitudinally propelled either into the transmission line ii and out of the transmission line it or vice versa, such propulsion being accomplished by turning of the shaft 8?}. The shaft 86 is provided with a gear wheel 32' which may engage a suitable motor drive.

Two generally cylindrical spring grip structures 83 and 89 are mounted on the conductor 83 in order to preserve the alignment of the rod 82 and to provide firm electrical contacts between therod'82'and the conductor Let it be assumed'that the transmission line H leads to one load andthetransmission line it leads to another load. The structure as which extends towards the transmission line H should then be approximately a quarter-wave length long andthe spring grip structure 88 which extends toward the transmission line 18"should be approximately a halfwave length long, dimensions given in terms of wave length having reference to electrical length. The central conductors 9i] and 9| of the trans mission lines 11 and 78 respectively are then so positionedthat they come almost to the ends of the spring grip structures as and 88 respectively. The ends-of the conductors 58 and Q! are hollowedout', preferably for substantially more than a half-wavelength. When the rod 82 extends for a half-wave length into the hollowed end of the conductor 9!, a transmission line is formed having the rod 82 and the conductor 9! as conductors and having an electrical length of a halfwave length. Since this transmission line is opencircuited at: its left hand end, because holiow portion of th'econductor 9! is considerably longer thanahalf-wavevlength, a high series impedance will bepresented by'the gap to the right of the end of the conductor 9i, thus preventing power from" proceeding down through the transmission line 18. Because'this gap is located at approximately a half wave length from the junction, the shunt/impedance ofiered by the transmission line H3 at the junction will be high and will exert relatively little interference with transmission of power from the transmission line 15 into the transmission line 17.

The rod 82 is of such" length that at the same time that'it extends approximately half-wave length into the hollow portion of the conductor 98,. it extends. approximately a quarter-wave lengthinto. the hollow portion of the conductor 98, thus providinga relatively low series impedance. at the gap at the leftehand end of the conductor 90 and allowing power to be transmitted into the transmission line. i? with practically no obstruction. As the rod 82 is gradually moved to the right, agradually increasing capacitive series impedance will be presented at the gap to the left of the conductor 95, while a gradually decreasing capacitive series impedance will be presented at the gap to therightof the end of the conductor 9 1.. The shunt impedance of the trans mission line 11, as seen. at the. approximate location of" the gap at the left end of the con-' ductor 90, will thus be capacitive, and as seen from the junction the shunt impedance will then be inductive, because of the intervening quarterwave length of line. The shunt impedance as seen from the junction of the transmission line 18 will be capacitive because the gap at the righthand end of the conductor 9! is located at a halfwave length from the junction. There will thus be some compensation between the reactive components of the shunt impedances, reducing the standing waves in the transmission line 15. This compensation is not complete, and becomes less complete as the rod 82 is moved to the right, for finally, when the rod 82 is inserted in the hollow part of the conductor 93 to the extent of a halfwave length, a high impedance is presented at the gap to the left or the end of the conductor 96, which causes a short circuit to appear at the junction. This type of device is therefore useful only for a limited range of variation of the power transmission to the transmission line 11 in the neighborhood of full transmission thereto, because when it is desired to transmit a relatively large proportion of power to the absorber through the transmission line 78, there will be a tendency for substantial standing waves to build up in the transmission line 15.

If the end of the conductor 5E3 were brought to a point about a half-wave length from the junction instead of to a point about a quarter-wave length from the junction, and the rod 82 were accordingly lengthened by a quarter-wave length, there would be no substantial mismatch of the line 75 at either extreme position of the rod 82, but the reactive component of the shunt impedance of the transmission lines ii and '58 as seen from the junction would both have the same sign so that a misrnacth would occur for intermediate positions of the rod 82. For the purpose of this invention, therefore, the arrangement shown in the figure is better than that just mentioned.

If desired the end of conductor 90 may be brought to a point about a half-wave length from the junction instead of to a point about a quarterwave length as disclosed above, and rod 82 may be likewise lengthened by a quarter wavelength at the end adjacent conductor 98. There will now be no substantial mismatch of line 15 at either extreme position of rod 82, but the reactive component of the shunt impedance of transmission lines TI and 78 as seen from the junction would both have the same sign so that a mismatch would occur for intermediate positions of rod 82.

It is to be understood in connection with the H power divider apparatus that whenever electrical lengths of a quarter or half wave length are specified, an odd multiple or even multiple, respectively, of a quarter wave length may be used equally as well. Likewise, where the term electrical length is used, it is to be understood as meaning a physical length of such value as to give the electrical eiTect of the corresponding electrical length in free space. Thus, the electrical lengths mentioned are to be taken as including the contribution of end effects. All distances referred to in terms of wave lengths are intended to be taken as electrical lengths as defined above.

Although I have shown and described only certain specific embodiments of the invention, I am fully aware of the many modifications possible thereof. Therefore, this invention is not to be limited except insofar as is necessitated by the prior art and the spirit of the appended claims.

What is claimed is:

1. A radio frequency power divider circuit, comprising an input coaxial transmission line having inner and outer conductors and being short circuited at one end thereof, a pair of coaxial output transmission lines also having inner and outer conductors, said outer conductors being joined to said input line at diametrically opposite points and at a distance of any odd multiple of a quarter wave length from said short circuited end, the mutually directed ends of said inner conductors of said output lines being hollowed out for a length greater than one-half Wave length, the difference in spacing of said ends from the inner conductor of said input line being an integral number of quarter wave lengths, a rod electrically joined to the inner conductor of said input line coaxially aligned with the inner conductors of said output lines and extending a predetermined distance into the hollowed portion of said inner conductors of said output lines.

2. A radio frequency power divider circuit, comprising an input coaxial transmission line having inner and outer conductors and being short circuited at one end thereof, a pair of coaxial output transmission lines also having inner and outer conductors, said outer conductors being joined to said input line at diametrically opposite points and at a distance of any odd multiple of a quarter wave length from said short circuited end, the mutually directed ends of said inner conductors of said output lines being hollowed out for a length greater than one-half wave length, a rod electrically joined to the inner conductor of said input line coaxially aligned with the inner conductors of said output lines and extending a predetermined distance into the hollowed portion of said inner conductors of said output lines, and means for varying the axial portion of said rod encompassed by each of said hollowed portions.

3. A radio frequency power divider circuit, comprising an input coaxial transmission line having inner and outer conductors and being short circuited at one end thereof, a pair of coaxial output transmission lines also having inner and outer conductors, said outer conductors being joined to said input line at diametrically opposite points and at a distance of any odd multiple of a quarter wave length from said short cir-.

cuited end, the mutually directed ends of said inner conductors of said output lines being hollowed out for a length greater than one-half wave length, a rod electrically joined to the inner conductor of said input line coaxially aligned with the inner conductors of said output lines and extending a predetermined distance into the hollowed portion of said inner conductors of said output lines, a rack provided at the central portion of said rod and a driving means associated with said rack for varying the axial portion of said rod encompassed by each of said hollowed portions.

4. A radio frequency power divider circuit, comprising an input coaxial transmission line having inner and outer conductors and being short circuited at one end thereof, a pair of coaxial output transmission lines also having inner and outer conductors, the outer conductors of said output lines being joined to the outer conductor of said input line at diametrically opposite points and at a distance of any odd multiple of quarter wave lengths from said short circuited end, the mutually directed ends of the inner conductor of said output lines being spaced substantially a distance of aquarter and a half wave length, re-

spectively, from the inner conductor of said input line and being hollowed out for a length substantially greater than a half wave length, a rod electrically joined to the inner conductor of said input line and extending into the hollowed end of said inner conductor spaced a half wave length for a distance of a half wave length and extending into the hollowed end of said conductor spaced a quarter wave length for a distance of a quarter wave length, a rack provided on the central portion of said rod, and a pinion rotatable by a shaft and connected to said rack for varying the axial position of said rod with respect to said hollowed ends, whereby the input power may be proportioned between the output transmission lines in accordance with the rotation of said shaft.

5. A radio frequency power divider comprising, an input coaxial line and two mutually directed output coaxial lines, each of said lines having relatively stationary inner and outer conductors, said outer conductors being joined to form a hollow T, the inner conductor of said input line penetrating to the junction of said hollow T, each of the inner conductors of said output lines also penetrating said T but being spaced from said junction, and a rod movable along the common axis of said output lines, said movable rod being in electrical contact with said inner conductor of said input line and in spaced, variable capacitive relationship with both of the inner conductors of said output lines.

6. A radio frequency power divider circuit, comprising an input coaxial transmission line having inner and outer conductors and being short-circuited at one end thereof, a pair of coaxial output transmission lines also having inner and outer conductors, the outer conductors of said output lines being joined to the outer conductor of said input line at diametrically opposite points and at a distance of an odd multiple of quarter wave lengths from said short-circuited end, the mutually directed ends of the inner conductors of said output lines being spaced substantially a distance of a quarter, and of a half wave length, respectively, from the inner conductor of said input line, means electrically connected to said inner conductor of said input line and capacitively coupled to said inner conductors of said output lines, and means for varying the position of said first-mentioned means to simultaneously vary the capacitive coupling between said first-mentioned means and said inner conductors of said output lines.

7. A radio frequency power divider comprising, an input coaxial line and two mutually directed output coaxial lines, each of said lines having an inner and an outer conductor, said outer conductors being joined to form a hollow T, the inner conductor of said input line penetrating to the junction of said hollow T, each of the inner conductors of said output lines also penetrating said T but being spaced from said junction by multiples of a quarter wave length, the mutually aligned ends of the inner conductors of said out put lines being hollowed out for a distance greater than a half Wave length, a movable rod disposed partially within said hollowed out ends of said inner conductors of said output lines in noncontacting relationship therewith, said movable rod having a length greater than the spacing between said mutually directed ends by an odd multiple of quarter wave lengths greater than one quarter Wave length, and means conductively coupling said movable rod to the inner conductor of said input line, said movable rod being movable axially of itself thereby to vary the coupling between said input coaxial line and said output coaxial lines.

8. A power divider as in claim 7 wherein said means conductively coupling said movable rod to said inner conductor of said input line comprises, first and second stub inner conductors rigidly secured to said inner conductor of said input line and extending to points adjacent the mutually directed ends of the inner conductors of said output lines, said movable rod being slidably journaled within said stub inner conductors.

RICHARD C. RAYMOND.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,228,692 Davies Jan. 14, 1941 2,401,863 Espley June 11, 1946 2,407,847 Peterson Sept. 17, 1946 2,410,657 Hershberger Nov. 5, 1946 2,411,553 Ramo Nov. 26, 1946 2,426,186 Dow Aug. 26, 1947 2,439,255 Longfellow Apr. 6, 1948 

